System and process for the analysis and predictive simulation of the temporal evolution of a hair region, and more particularly of the human scalp

ABSTRACT

System and process for the analysis and predictive simulation of the temporal evolution of a hair region, and more particularly of the human scalp System for the simulation of the evolution of a region of the scalp of a subject over time, comprising a means of observation of the said hair region able to output digital observation data, a first digital data processing means capable of classifying elementary parts of the said region on the basis of the observation data, a second digital data processing means capable of simulating the evolution of the said hair region as a function of the data emanating from the first digital data processing means, and a means of displaying the data emanating from the second digital data processing means.

[0001] The present invention relates to the field of cosmetics and moreparticularly to the evolution of the human head of hair over the courseof a lifetime.

[0002] The phenomenon of hair growth and loss in the human species, moreparticularly in the male sex, is complex and differs from animal speciesthrough at least two criteria:

[0003] there are very few animal species which, with age, progressivelylose their fur;

[0004] animal species may experience seasonal moulting on account of thefact that the cycles of the strands are synchronized, that is to say allthe strands grow or are lost at the same time.

[0005] In man, the hairs are generated by the hair follicles implantedin the scalp. A healthy head of hair is said to contain between 100 000and 150 000 hairs, and each hair within this head of hair possesses itsown cycle.

[0006] This life cycle is broken down into three generally successivephysiological phases:

[0007] a phase of hair growth, referred to as Anagen (A), which may lastfrom a few weeks to 10 years,

[0008] a transient phase of involution of the follicle and ceasing ofhair growth with degeneration of the root, known as Catagen, of theorder of a few weeks,

[0009] a phase of shedding of the hair with the root moving up towardsthe surface, known as Telogen (T), lasting 1 to 5 months.

[0010] At the end of this last phase, the hair therefore disappears fromthe scalp and this Disappearance (D) may extend from a few days to a fewmonths before the follicle is reactivated to give a new hair in theanagen growth phase.

[0011] After a certain number of cycles, the follicle permanently ceasesits production and the hair may be regarded as Dead (Dd).

[0012] Given the ratio of the durations of the various phases of thelife cycle of the hair, in practice, the Catagen phase which is theshortest is rarely observed; this is why the person skilled in the artprefers to reckon the Anagen (A), Telogen (T) and Disappearance (D)phases. FIG. 2 shows how these phases are strung together in the courseof the hair's cycle.

[0013] The phenomenon of ageing, over the course of a lifetime, leadsover about ten years to a shortening of the growth phases (A) andconsequently to an increase in the proportion of the hairs in the lossphase (T). This phenomenon may be accelerated in the case of alopeciawhich more particularly afflicts men but also women, and which in itsfinal stage leads to baldness, or total shedding of the head of hair.

[0014] Since the phases of the hair cycle unravel over long durations,especially the growth phase (A), it follows that the observation of thestate of the hairs of a region of the scalp at a precise instantconstitutes merely an instantaneous measurement which cannot forecastthe future evolution.

[0015] Specifically, the current state of the art does not make itpossible by observing and quantifying the state of the hair of a young25-year-old person to forecast and/or illustrate what the state of hishead of hair will be when he reaches 60 years of age.

[0016] The aim of the present invention is to simulate the chronologicalevolution of a head of hair on the basis of the smallest possible numberof measurements.

[0017] The system, according to the invention, is intended for thesimulation and for the predictive analysis of the evolution of a regionof the scalp of a subject over time, and whose extension to the entirescalp makes it possible to illustrate the overall evolution of the headof hair.

[0018] The system comprises a means of observation of the said hairregion able to output digital observation data, a first digital dataprocessing means capable of classifying elementary parts of the saidregion on the basis of the observation data, a second digital dataprocessing means capable of simulating the evolution of the said hairregion as a function of the data emanating from the first digital dataprocessing means, and a means of displaying the data emanating from thesecond digital data processing means, the data output by the firstprocessing means comprising at least one classification according to theduration of the phases of the hair cycle.

[0019] Advantageously, the observation data, output by the firstprocessing means, comprise the surface density of hairs, the proportionA (as a %) of hairs in the anagen phase, the proportion T of hairs inthe telogen phase (as a %), the proportion D of disappeared hairs (as a%), the proportion Dd of dead hairs (as a %) and the individual rate ofgrowth of the hairs.

[0020] Advantageously, the second processing means comprises a means forapplying to each observed hair a duration of continuation in itsprevailing phase, on the basis of a statistical distribution of thephase durations and of a random number. The distribution is of thelog-normal or negative-exponential type or else bell-shaped with theform illustrated in FIG. 3.

[0021] In one embodiment of the invention, the second processing meanscomprises a means for estimating the number of cycles n_(c) performed byan observed hair, and for comparing it with a predetermined maximumnumber of cycles N_(k), a cycle being defined by the successive passagethrough the three states, anagen, telogen and disappeared.

[0022] In one embodiment of the invention, the second processing meanscomprises a matrix of probabilities of transition from one phase toanother phase.

[0023] In another embodiment of the invention, the second processingmeans comprises a means for allocating a given duration of phase to ahair.

[0024] The means for allocating a given duration of phase to a haircomprises a random number generator and a means for comparing the saidrandom number with aggregate probabilities of phase transition.

[0025] In one embodiment of the invention, the second processing meanscomprises a matrix representative of the influence of data relating toneighbouring hairs on the transition from one phase to another phase.

[0026] In one embodiment of the invention, the second processing meanscomprises a table representative of the evolution of the mean values ofduration of the anagen, telogen and disappearance phases.

[0027] In one embodiment of the invention, the system comprises a meansfor performing a third processing for simulating the evolution of theentire head of hair of the subject on the basis of the data emanatingfrom the second processing.

[0028] In one embodiment of the invention, the system comprises a meansfor associating data from simulating the head of hair which may possiblybe associated with other data relating to the evolution of other sites,for example, the face, especially the evolution of the number ofwrinkles, the modifications from ageing of the face, any clinical signassociated with ageing with the data emanating from the third processingmeans.

[0029] The subject of the invention is also a process for the simulationand predictive analysis of the evolution of a region of the scalp of asubject over time, in which:

[0030] the said hair region is observed so as to provide observationdata. The said observation may comprise any appropriate means forcollecting photographic and videographic, analogue or digital images orany other means of imaging obtained through a physiology-friendlynon-invasive route, including those requiring no particular preparationof the scalp,

[0031] a first digital processing of the observation data is performedso as to classify elementary parts of the said region,

[0032] a second digital processing is performed so as to perform asimulation of the temporal evolution of the said hair region as afunction of the data emanating from the first digital processing means,and

[0033] data emanating from the second digital processing are displayed.

[0034] Advantageously, at least two observations are performed separatedby a first given duration, each observation being preceded by a step ofshaving the said hair region, the shaving step being separated from thecorresponding observation by a second given duration, in such a way thatan evolution of the said hair region can be noted.

[0035] The first given duration may lie between one and ten weeks,preferably between two and six weeks, for example of the order of onemonth. The second given duration may lie between one and ten days,preferably less than five days, for example of the order of two days.

[0036] The said hair region may undergo, during a first observation, amarking remaining visible at least Up to a second observation.

[0037] In one embodiment of the invention, the observation data comprisethe surface density of hairs, the proportion A of hairs in the anagenphase, the proportion T of hairs in the telogen phase, and theindividual rate of growth of the hairs.

[0038] Preferably, the second digital processing takes into account theratios of the durations of the anagen and telogen phases.

[0039] Advantageously, a third digital processing is performed so as toperform a simulation of the temporal evolution of the entire head ofhair of the subject on the basis of the data emanating from the seconddigital processing and the data emanating from the third digitalprocessing are displayed.

[0040] The displaying of the said data emanating from the third digitalprocessing can be performed by flat projection, for example as aprojection of the type used in cartography, especially a conical Lambertprojection.

[0041] Data from simulating the evolution of the face (method known asmorphing) may possibly be associated with the data emanating from thethird digital processing and the associated data may possibly bedisplayed.

[0042] In one embodiment of the invention, it is also possible tosimulate the evolution of a region of the scalp which has undergone amodification of aesthetic type.

[0043] The observation data may emanate from a phototrichogram,videotrichogram or any other non-invasive method making it possible toassess the state of the cycles of the observed hairs.

[0044] Stated otherwise, the simulation system associates theestablishing of initial observation data, on the basis of a region ofsmall area, regarding the number of hairs, the proportions of the latterin each phase, the duration of their respective cycles, the mathematicalmodelling of the latter which makes it possible to extend the evolutionof each parameter to the short, medium or very long term, and theapplication of this modelling to the extension of the entire head ofhair for display by an imaging means.

[0045] The state of the head of hair can be simulated over variousdurations lying between 3 months and 100 years, with the aim ofpredicting its natural evolution or its evolution modified by externalor internal causes.

[0046] The present invention will be better understood on studying thedetailed description of a few embodiments taken by way of whollynon-limiting examples and illustrated by the appended drawings in which:

[0047]FIG. 1 is a diagrammatic view of the simulation system inaccordance with the invention;

[0048]FIG. 2 is a diagrammatic view showing the evolution of the hairsbetween the various phases; and

[0049]FIG. 3 is a log-normal type distribution curve.

[0050] As may be seen in FIG. 1, the simulation system in accordancewith the invention comprises a camera 1, for example of CCD type,equipped with an objective 2, intended for observing a specified hairregion, for example a region of 1 cm² or the entire head of hair.

[0051] The system also comprises a classification means 3 receiving thedigital data emanating from the camera 1.

[0052] The classification means 3 is provided with a memory 4 allowingamong other things the storage of the said data originating from thecamera 1.

[0053] The classification means 3 is capable of determining the anagen,telogen or disappeared state, in which the hair can be catalogued in anelementary part of the observed region of the scalp.

[0054] Stated otherwise, the classification means 3 receives as input animage file representative of the hair region observed and in which eachelementary zone is assigned a grey level or colour characteristics, andoutputs a file in which each elementary zone is assigned a state,anagen, telogen or disappeared, and possibly other characteristics.

[0055] It should be noted that an elementary zone output by theclassification means 3 may group together several pixels of the imagecaptured by the camera 1.

[0056] The simulation system comprises a simulation means 5 providedwith a memory 6 and linked to the classification means 3 so as toreceive the classified data comprising in particular the two-dimensionalcoordinates of a hair follicle, the prevailing phase of thecorresponding hair together with the rate of growth of the said hair.

[0057] The classification means 3 can also transmit to the simulationmeans 5, data relating to the surface density of hair, to the proportionA of hairs in the anagen phase, to the proportion T of hairs in thetelogen phase, to the proportion D of disappeared hairs, and to theproportion Dd of dead hairs.

[0058] The simulation means 5 is capable of outputting data forforecasting the individual state of each hair at a future instant.

[0059] Stated otherwise, the simulation means 5 provides a filecontaining the coordinates of a hair follicle, the phase which thecorresponding hair will be in at a future date, and the date for whichthe simulation was carried out.

[0060] The system furthermore comprises a means 7 for generalizing thesimulation to the entire head of hair of a user.

[0061] On the basis of the simulation data originating from thesimulation means 5, of which the data generally relate to only a smallarea, for example of the order of 1 cm², the generalization means 7 isable to output data similar to those provided by the simulation means 5but covering a larger expanse desired by the user, for example theentire scalp.

[0062] The generalization means 7 also receives data originating fromthe classification means 3 insofar as the camera 1 will, with the aim ofgeneralization, capture at least one general image of the area inrespect of which one wishes to perform the generalization, in particularthe scalp, so as to be able to extend the results of the simulation tothis larger area.

[0063] A display means 8 such as a monitor, provided with a screen 9, islinked to the generalization means 7 so that the user can see theresults of the simulation just performed.

[0064] A printer, not represented, could also be provided and linked tothe generalization means 7.

[0065] Represented in FIG. 2 is the possible evolution of the phases ofa hair.

[0066] A given hair which is in the anagen phase A, that is to say thegrowth phase may, over a given elementary duration, remain in this samephase or evolve towards the telogen phase T or ceasing of growth phase.

[0067] The passage of the hairs from the anagen phase A to the telogenphase T is a phenomenon which is analysed statistically by consideringthat the hairs remain in the anagen phase A for a duration whose mean isequal to μ_(A) and whose standard deviation is equal to σ_(A).

[0068] The hairs remain in the telogen phase T for a duration whose meanis μ_(T) and whose standard deviation is σ_(T) and normally evolvetowards the disappearance state D.

[0069] The hairs remain disappeared for a duration having mean μ_(D) andstandard deviation σ_(D) and thereafter evolve either towards a newanagen phase A, or towards a death phase Dd in which they remainpermanently.

[0070] The head of hair is modelled by a discrete network whichrepresents its surface. The number of points or nodes of this networkcorresponds to the number of hair follicles. Typically, for asimulation, the evolution of some 100 hair follicles will be taken intoaccount.

[0071] The follicular automaton model characterizes each follicle by itsspatial position within the network, its state (A, T, D, Dd) , theremaining duration of its stay in the relevant phase as well as thenumber of cycles performed by this follicle.

[0072] The term cycle is understood to mean the passage of a folliclethrough the three states, anagen, telogen and disappeared, with returnto the anagen phase.

[0073] The follicles are considered to evolve independently of theirneighbours and the time is taken to be a discrete variable which can becounted in months, or even weeks.

[0074] The duration of the anagen, telogen and disappearance phases ischaracterized by distributions whose mean values μ_(A), μ_(T), μ_(D),and standard deviations μ_(A), μ_(T), μ_(D) are determined on the basisof experimental data which will have been stored in the system.

[0075] The mathematical form of distribution for the duration x of thevarious phases will be a distribution of negative-exponential type orpreferably a log-normal distribution.

[0076] The log-normal distribution function may be written:${f\left( {{x;\mu},\sigma} \right)} = {\frac{1}{x\sqrt{2{\pi\sigma}}}{\exp \quad\left\lbrack {{- \frac{1}{2\sigma^{2}}}\left( {{\log \quad x} - \mu} \right)^{2}} \right\rbrack}}$

[0077] At the beginning of the simulation, the initial state of eachfollicle is fixed: start phase (A or T or D), number of follicularcycles n_(c) already performed by each follicle, mean and standarddeviation of each distribution, duration of the first phasecorresponding to the chosen distribution.

[0078] The model is then made to evolve iteratively via time steps,equal for example to one month.

[0079] The modelled follicles are tested to determine those for whichthe moment has arrived to perform the next transition.

[0080] These follicles pass to the next state in the sequence of thecycle A→T→D→A.

[0081] The number of complete cycles performed by each follicle iscounted.

[0082] If a follicle has reached a critical number of cycles N_(k), itdies and passes to the state Dd where it remains permanently. N_(k) is,in general, between 20 and 25.

[0083] The parameters of the model may possibly evolve over time.

[0084] The duration of the various phases A, T or D can decrease orincrease according to hypotheses which may be added.

[0085] For each time step, the proportions of follicles in the variousstates A, T, D or Dd are calculated.

[0086] The number of follicular cycles performed by each of thefollicles is calculated.

[0087] Then, we return to the first step of incrementing the discretetime variable until the final duration of the simulation is reached.

[0088] One thus succeeds in reproducing behaviours which arequalitatively and quantitatively in agreement with the experimentalobservations.

[0089] This modelling reproduces the distribution of the follicles inphases A, T and D.

[0090] By way of example, it is found that alopecic individuals arecharacterized, among other things, by shorter mean durations of theanagen phase than individuals not suffering from alopecia.

[0091] For alopecic individuals, this is manifested as a smallerfraction of hairs in the anagen phase than for the others.

[0092] It is interesting to make the mean duration of the anagen phaseevolve over time by providing a law of decrease.

[0093] By virtue of the model, it is possible to simulate the long-termeffect of an increase or of a reduction in the mean duration of thevarious phases.

[0094] It is then possible to track the appearance of alopecia or itsdisappearance according to the hypotheses considered, and thus simulatethe effect of various internal or external factors.

[0095] The model also makes it possible to envisage the consequences ofthe death of the follicles after a critical number N_(k) of follicularcycles for a given individual.

[0096] The hypothesis is created that each follicle can perform only afinite number of cycles.

[0097] As a result, the shorter the durations of the anagen phases, themore marked is the tendency for the hairs to be lost permanently.

[0098] The mean duration of the anagen phases will be a function whichwill depend on the spatial position of the hair on the scalp of theuser, this function being implemented by the generalization means 7 ofFIG. 1.

[0099] By way of example, a mean duration μ_(A) of the anagen phase canbe assigned a duration of three months at the vertex, a region which isliable to be affected by alopecia, and of 20 months on the sides, aregion which is appreciably less prone to alopecia.

[0100] Stated otherwise, the evolution of a hair is modelled by thefollowing array. I J State n_(c) Duration 15 15 A 3 6 15 15 A 3 5 15 15A 3 4 15 15 A 3 3 15 15 A 3 2 15 15 A 3 1 15 15 A 3 0 15 15 T 3 2 15 15T 3 1 15 15 T 3 0 15 15 D 3 3 15 15 D 3 2 15 15 D 3 1 15 15 D 3 0 15 15A 4 10 

[0101] With I and J, the spatial coordinates of the follicle and n_(c)the number of cycles which it has performed. On the basis of anobservation carried out on the number of cycles n_(c) at the instant ofion is estimated in accordance with the age of and the state of theirhead of hair, or possibly the scalp insofar as the latter may exhibit,with age and alopecia, a few disorders or anomalies of pigmentationand/or of relief which can be detected by the observation means.

[0102] The duration of each cycle which is assigned to each transitionresults from the drawing of a random number x performed using a randomnumber generator provided in the simulation means and to which thelog-normal function is applied in such a way as to determine the saidduration assigned to a given phase.

[0103] The variable n_(c) is incremented with each transition from thedisappeared state D to the anagen phase A. When n_(c) becomes equal tothe critical number of cycles N_(k), then the hair passes to the deathphase Dd where it remains permanently.

[0104] For a user, two observations will therefore be performedseparated by a specified duration, for example of the order of onemonth.

[0105] In the case, for example, of observations carried out with thevideotrichogram technique, the procedure may be as follows:

[0106] an area of the scalp of the order of a cm² is completely shavedand then, a few days later, for example two or three, a snapshot of thesaid area which was shaved is captured by means of the camera 1.

[0107] It is thus possible, by virtue of the classification means, todetermine which phase each hair is in.

[0108] Specifically, the hairs in the anagen phase will have grownappreciably, the hairs in the telogen phase will not have grown or willhardly have grown, the disappeared hairs and the dead hairs will betemporarily or permanently absent.

[0109] After the predetermined duration, for example of the order of 1to 3 months, a second videotrichogram is performed according to the sameprocedure.

[0110] Thereafter, by comparing the two videotrichograms, a meanduration and a standard deviation of each phase are thereby determined,thus making it possible to operate the model.

[0111] In the follicular automaton model, there may also be provision tomake the means μ_(A), μ_(T) and μ_(D) evolve, on the basis of theinitial data gathered using the videotrichograms, as a function of thenumber of cycles already performed n_(c), by providing for theprogressive shortening of the mean durations.

[0112] To improve the quality of the generalization performed by thegeneralization means 7 of FIG. 1, it will be possible always to performthe observations at the same place on the scalp of all the users in sucha way as to be able to apply the same generalization to all.Alternatively, the spatial coordinates of the hair region subjected tothe observations will be indicated to the generalization means 7 so asto allow the effective and realistic simulation of the evolution of theentire head of hair, and to do so over several years, or even tens ofyears.

[0113] The user benefits from a forecast at various times, from 6 monthsto 100 years for example.

[0114] This forecast can also pertain to indirect parameters such as thecoverage of the head of hair in addition to the phase parameters, and becoupled with a simulation of the evolution of the face, for example ofthe number of wrinkles, of the sagging of the eyelids and of anyclinical sign associated with ageing.

1. System for the simulation and predictive analysis of the evolution of a region of the scalp of a subject over time, characterized in that it comprises a means of observation of the said hair region able to output digital observation data, a first digital data processing means capable of classifying elementary parts of the said region on the basis of the observation data, a second digital data processing means capable of simulating the evolution of the said hair region as a function of the data emanating from the first digital data processing means, and a means of displaying the data emanating from the second digital data processing means, the data output by the first processing means comprising at least one classification according to the duration of the phases of the hair cycle.
 2. System according to claim 1 , characterized in that the observation data, output by the first processing means, comprise the surface density of hairs, the proportion A of hairs in the anagen phase, the proportion T of hairs in the telogen phase, the proportion D of disappeared hairs, the proportion Dd of hairs in the dead phase and the individual rate of growth of the hairs.
 3. System according to claim 2 , characterized in that the second processing means comprises a means for applying to each observed hair a duration of continuation in its prevailing phase, on the basis of a distribution of the phase durations and of a random number.
 4. System according to claim 2 or 3 , characterized in that the second processing means comprises a means for estimating the number of cycles n_(c) performed by an observed hair, and for comparing it with a predetermined maximum number of cycles N_(k), a cycle being defined by the successive passage through the three states, anagen, telogen and disappeared.
 5. System according to any one of claims 2 to 4 , characterized in that the second processing means comprises a matrix of probabilities of transition from one phase to another phase.
 6. System according to any one of claims 2 to 4 , characterized in that the second processing means comprises a means for allocating a given duration of phase to a hair.
 7. System according to claim 6 , characterized in that the means for allocating a given duration of phase to a hair comprises a random number generator and a means for comparing the said random number with aggregate probabilities of phase transition.
 8. System according to any one of claims 2 to 7 , characterized in that the second processing means comprises a matrix representative of the influence of data relating to neighbouring hairs on the transition from one phase to another phase.
 9. System according to any one of claims 2 to 8 , characterized in that the second processing means comprises a table representative of the evolution of the mean values of duration of the anagen, telogen and disappearance phases.
 10. System according to any one of the preceding claims, characterized in that it comprises a means for performing a third processing for simulating the evolution of the entire head of hair of the subject on the basis of the data emanating from the second processing means.
 11. System according to claim 10 , characterized in that it comprises a means for associating data relating to the evolution of other sites with the data emanating from the third processing means.
 12. Process for the simulation and predictive analysis of the evolution of a region of the scalp of a subject over time, in which: the said hair region is observed so as to provide observation data, a first digital processing of the observation data is performed so as to classify elementary parts of the said region, a second digital processing is performed so as to perform a simulation of the temporal evolution of the said hair region as a function of the data emanating from the first digital processing means, and data emanating from the second digital processing are displayed, the data output by the first processing means comprising at least one classification according to the duration of the phases of the hair cycle.
 13. Process according to claim 12 , in which at least two observations are performed separated by a first given duration, each observation being preceded by a step of shaving the said hair region, the shaving step being separated from the corresponding observation by a second given duration, in such a way that an evolution of the said hair region can be noted, the observation data comprising the surface density of hairs, the proportion A of hairs in the anagen phase, the proportion T of hairs in the telogen phase, and the individual rate of growth of the hairs.
 14. Process according to claim 13 , in which, on the basis of the observation data, the hair coverage produced per unit time and area is calculated.
 15. Process according to any one of claims 12 to 14 , in which the second digital processing takes into account the ratios of the durations of the anagen and telogen phases.
 16. Process according to any one of claims 12 to 15 , in which a third digital processing is performed so as to perform a simulation of the temporal evolution of the entire head of hair of the subject on the basis of the data emanating from the second digital processing and the data emanating from the third digital processing are displayed by flat projection.
 17. Process according to claim 16 , in which, data from simulating the evolution of the face are associated with the data emanating from the third digital processing and the associated data are displayed. 